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C. Lift motor rotation sensor (E1CLK, E2CLK), remaining amount sensor (RESTR,F), side sensor input circuit
The lift motor rotation sensor senses rotation of the lift motor, and it is composed of the slit disc attached to the rotating shaft of the lift motor and the
photo interrupter. When the motor rotates, pulse signals are provided by the sensor. The remaining amount sensor senses the remaining amount of
paper in the paper tray 3, and is composed of the photo interrupter and the shield plate provided with the mechanism which operates with the height
of the lifter plate of the paper tray 3. The table below shows the truth table of the remaining amount sensor. The side sensor senses open/close of
the cover which removes paper jams in the paper transport path.
The circuit compositions of the rotation sensor, the remaining amount sensor, and the side sensor are the same as that of the limit sensor as shown
in (b).
Remaining amount sensor
REST1, 2
D. Resist sensor (RSEN1, 2) input circuit
The resist sensor is the photo transistor positioned in front of the roller which is in the transport path of paper discharged from the paper tray 3 and
the paper tray 2, and is provided with the lever. The transported paper pushes the lever to move it off the sensor slit, and the paper arrival is
detected. RSEN1 and TSEN2 are of the same circuit composition. The following description is made on RSEN1.
The photo interrupter is composed of the LED and the photo transistor (open-collector output). A current limited by R25 flows through the LED,
which is always lighted. When the lever enters the photo interrupter slit, the infrared light from the LED is shielded to turn off the photo transistor
(output high impedance). At that time, the signal of RSEN1 becomes HIGH (5V). When the lever is off the slit, the photo transistor is turned on to
drive the signal of RSEN1 LOW (0V). R70 and C15 form a noise filter. IC8.4 rectifies the input waveform.
77
8
9
P26
IC8-4
E. Size switch (SIZESW) input circuit
This is a 3-contact slide switch to switch the paper size (A4, B5, LTR) of the paper tray 3, and is attached to the frame on the left side of the front.
The signals are from three lines, and they are HIGH (5V) when ON. The signals of three lines are converted into 2bit by IC6.2, 3. R16, 17, and 21
are pull-down resistors and R22, R23, and R24 are the input protection resistors for IC6.
The truth table is shown in the table below.
B5
A4
Letter
20
6
P67
IC6-2
21
8
P66
IC6-3
Paper remaining amount: 0 ∼ 750 sheets
Shield plate ON
Signal level LO (0V)
+5V
R69
15K
R70
1.0K
C15
1000pF
GROUND
P67
P66
Hi
Lo
Hi
Hi
Lo
Hi
R22
47K
4
R23
5
47K
9
10
R16
10K
GROUND
Paper remaining amount: 750 ∼ 1500 sheets
Shield plate OFF
Signal level HIGH (5V)
+5V
R25
390
4
DC5V
CN8-4
6
REG_SEN1
CN8-6
5
SG
CN8-5
GROUND
Control PWB
SEN1 input circuit
CN9-2
Hi
Lo
Lo
+5V
1
+5V
2
B5
3
A4
4
R24
LETTER
47K
R17
R21
10K
10K
GROUND
GROUND
Control PWB
SIZES input circuit
11 – 3
LED-A
CN-3
REG_SEN1
CN-2
SG
CN-1
RSEN1
CN9-3
Lo
Hi
Lo
CN9-1
3pin
CN9-2
1pin
CN9-3
2pin
CN9-4
4pin
7pin
5pin
6pin
8pin
SIZESW
CN9-4
Lo
Lo
Hi
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